philiow313 Posted April 7, 2004 Share Posted April 7, 2004 how much PSI could a turbo L28 motor take with forged dished pistons and forged con. rods? hit me with some other variables as well, please. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted April 7, 2004 Share Posted April 7, 2004 Depends on efficiency of the intercooler and its' size, and how well you can control fuel and ignition. Quote Link to comment Share on other sites More sharing options...
philiow313 Posted April 7, 2004 Author Share Posted April 7, 2004 say stock with no IC Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted April 7, 2004 Share Posted April 7, 2004 Not meaning to sound sarcastic here, but running "stock with no IC" does not require foged anything. One is better off taking the money you would spend on forged internals and spend it on quality bolt-ons that allow you to run almost twice the boost, SAFELY than you could with "stock with no IC". Having forged internals does not make the "stock with no IC" state of tune run more boost. What it will do is safeguard you against detonation better but you should always be tuning to avoid any detonation. Quote Link to comment Share on other sites More sharing options...
philiow313 Posted April 7, 2004 Author Share Posted April 7, 2004 Thanks Scottie. I understand that, a friend of mine is actually looking into doing this swap into his 240 (assuming he gets it haha). We are just kinda throwing ideas out there for what to do. So what then, with a decent IC, would you be able to run with everything else pretty much stock? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 7, 2004 Share Posted April 7, 2004 I agree with Scottie... Even with forged internals, detonation is detonation and can still destroy a motor very rapidly in a turbo charged car. What PSI it takes to get detonation on a ZXT motor depends on what you're using from fuel control... 10psi is about the limit on stock EFI (many say even that is pushing it... indeed I run 10psi w/o an I/C and on the dyno I was running lean above 5000rpm at 13:1... pretty much the ragged edge of safety). But even with programmable EFI pushing plenty of fuel and pulling lots of timing out on top, I wouldn't think you could push more than 12 or maybe 15psi tops on pump gas w/o an I/C. If you were running that kind of boost, non intercooled, out of the stock T3 turbo, you're going to be running horribly inneficiently, the turbo blowing super hot air, so even if you could get enough fuel and timing retard to make it safe, you wouldn't be making good power from it. But I too have to wonder... why would you even bother with this or where did you get the idea to go that route first? The stock L28et bottom end is stout and reliable and can make lots of power, most agree up to about 350hp at the wheels reliably. To get there you would need a good I/C, plenty of fuel (bigger injectors, upgraded fuel pump, most likely some programmable EFI) and a better turbo, a T3/04... you should be spending your money on those things instead of putting big bucks into expensive forged parts. With a good I/C and enough fuel, detonation should not be an issue, even up into the big boost numbers, 18-20psi not being too uncommon, hence you just wouldn't need forged internals unless you were going for BIG power, 400+hp, and by that point it would be just plain silly to be running w/o an I/C anyways. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 7, 2004 Share Posted April 7, 2004 by the way, even with an I/C, the stock 280zxt EFI is no good for boost levels much over 9-10psi. The injectors can handle it (they should be good up to about 250hp) but the stock ECU is very limited in it's ability to compensate for the increased airflow and oxygen present when you turn up the boost and cool down the intake charge with an I/C. The stock air flow meter only measures the air flow at wide open throttle, up to about 4000rpm. After that, it's only working using preset fuel and timing maps, based on RPM, head temp, and air temperature as measured at the airflow meter... those maps were designed to accomodate 9psi at most, as this is where the factory pop-off valve would vent making it impossible to run more boost than that anyways. Every dyno chart I've seen on 280zxt motors running boost higher than 9psi, on stock EFI w/o some mod to add fuel, always starts to run lean at aroudn 4500-5000rpm, and it's actually worse on intercooled cars, as the colder air packs more oxygen, leaning out the mixture even more... Tyson280zx was running way lean when he dynoed, running only 8psi, after he installed his I/C. But you dont have to do much to make it safe. First you will need an upgraded fuel pump, and then some way of getting more fuel into the mix at higher rpm's... you can either go the cheap way and get an adjustable fuel pressure regulator and up the fuel pressure some, or you can get bigger fuel injectors. Then you tune that extra fuel OUT in the low and mid RPM ranges by adjusting the spring tension in the airflow meter, making it see less air in the RPM ranges that it effects (again, only up to about 4000rpm). If you just want to run bone stock, no I/C, no added fuel, which is pretty much what I'm doing right now, 9-10psi is the safety limit, but you'll have to keep an eye on the revs... I wont take it above 5500... and rarely even that high. But that's not such a bad compromise as the engine's power band is between 3000-5000 anyways and there's just really not much point to rev it much past that as the power falls way off after that. I make good power running like this... in a very light 240 it makes for a pretty quick car, but I do plan on installing an I/C at some point, as well as a fuel pressure regulator to get some more fuel. one cheap mod you should consider absolutely necessary is a BOV... not only because it does help performance a little by letting your turbo stay spooled between shifts (w/o it back pressure builds up rapidly when the throttle snaps shut, exerting a lot of force when it tries to blow back thru the turbo, slowing it down) but it also extends the life of the turbo (because that same back pressure on the compressor puts a lot of strain on it wearing the bearings out rapidly). Quote Link to comment Share on other sites More sharing options...
philiow313 Posted April 7, 2004 Author Share Posted April 7, 2004 Wow a lot more information than I expected. Thanks guys! My friend who has this idea isnt too performance smart, he just knows a few things and wants to go fast I only knew a little, but I knew if i just posted this question I'd get an answer for him, mostly. I knew you'd need more than just forged internals, but I wasn't sure all of the things you'd need to up the boost. BTW, what kinda hp/tq increases did you get from upping the boost to 8,9, or 10 psi with everything else stock, or with an IC? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 8, 2004 Share Posted April 8, 2004 heheh I tend to be really long winded with my replies guess that's because that's how I like them... the more info and details the better. Well, with a stock T3 turbo and stock motor, no I/C, you gain about 15hp/15ft lbs per psi for the first couple psi increase... as the boost goes up however, the amount of increase goes down... like only 10hp from 9 to 10psi... and then because the T3 becoms so horribly inneficient after that, down to like 5hp or even less with every PSI increase after that. The I/C will help with that a bit, keeping it from tapering off so fast, but it still definately tapers off. A bone stock 280zxt puts down about 145-150hp and 165-170ft lbs on the dyno at about 7psi. I'm running 10psi on pretty much bone stock setup, and put down 200hp and 234ft lbs, so 50hp increase and 65 ft lbs increase from 3 psi. A pretty nice gain from stock just using a $10 boost controller and just turning the knob, eh? Quote Link to comment Share on other sites More sharing options...
philiow313 Posted April 8, 2004 Author Share Posted April 8, 2004 Wow thats good. Just for my own future reference, where do I buy this boost controller? Quote Link to comment Share on other sites More sharing options...
Dnaught14 Posted April 8, 2004 Share Posted April 8, 2004 There are tons of boost controllers out there,,,just look around. I personally would say that before you start to do anything you get a better grasp of how the car works and what you want out of it. It seems to me like you have little if any knowlege about turbo applications or the z,,which is cool, everyone starts somewhere. I suggest reading everything you can on this website, and any other info you can find. if you have any questions do a search for it first. Odds are someone has been there before. Good Luck with your possible build. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 8, 2004 Share Posted April 8, 2004 check out dawesdevices.com (I may not be spelling that right...) they sell it for about $50 I think ready to go... personally I wouldn't buy it from them, but you can see what it is and what it does. It aint pretty, but it works. Only disadvantage over most fancier units is that you have to pop the hood to change the boost... a lot of people prefer to be able to adjust boost from inside the car while driving. Personally I think that would just get me in trouble so it works fine for me The advantage is that those fancy units cost $200 and up. You can build the exact same thing that dawesdevices is selling for about $15. I ordered the parts from mcmaster-carr online. Only thing is you will need a pin vice and an extremely small drill bit, .020" for a vent hole you need to drill. If you actually get a turbo car, or your friend or whatever, and want to put one of these together let me know and I'll look up the part #'s for you. Quote Link to comment Share on other sites More sharing options...
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